A 9-year-old boy who wandered from his father’s side may have opened a new chapter in the evolutionary story of mankind when he found the fossilized collarbone of a child who lived almost 2 million years ago.
Matthew Berger was about 15 meters (49 feet) from his dad, Lee, a paleontologist working at the archeological dig in South Africa known as the Cradle of Humankind, when he called out, his father said during a briefing yesterday with reporters.
“Dad, I found a fossil,” the youngster said. The bone was just “sticking out of the rock,” the elder Berger said. Scientists now suspect Matthew discovered a new species of hominid, the name for humans and their extinct ancestors, that lived just prior to the historical development of modern man. Researchers reported finding partial skeletons of the male child and an adult female who lived 1.78 million to 1.95 million years ago in two papers published today in the journal Science.
The new species “might be a Rosetta Stone to defining just what the genus Homo is,” Berger, a professor at the University of the Witwatersrand, in Johannesburg, said in the call with reporters. “This is a good candidate for being the transitional species between the southern African ape-man” and later groups more closely related to modern humans.
The male child and the adult female would have been alive about 1 million years after “Lucy,” one of the best-known primitive human ancestors. The scientists said the species, named Australopithecus sediba, include a mix of characteristics belonging to more primitive and more advanced humans and may represent one of the most recent ancestors leading to those in the Homo genus, the group to which modern humans belong.
Australopithecus means “southern ape” and refers to an early human species that includes Lucy, who is 3.2 million years old and was discovered in Ethiopia in 1974. Sediba means “natural spring” or “fountain” in the South African language Sotho, an “appropriate name for a species that might be the point from which the genus Homo arises,” Berger said.
The female adult and male child are estimated to have been about 1.27 meters (4.17 feet) tall, and to have weighed 33 kilograms (73 pounds) and 27 kilograms, respectively. The female was likely in her late 20s or early 30s, while the child was probably 8 years old to 13 years old, the scientists said.
While the species has long arms, similar to apes, it has short, powerful hands, unlike the longer fingers of chimpanzees. Its long legs and more developed pelvis indicate it was able to walk upright, yet still likely spent some of its life in trees, according to the researchers.
One of the most surprising aspects of the discovery helped convince the researchers that the two skeletons weren’t in the Homo genus: the small skull, Berger said.
“It would look almost like a pinhead,” Berger said. The size of the cranium indicated this species had brains as small as some of the oldest “ape-men,” yet their faces more closely resembled something similar to Homo erectus, a more direct human ancestor, he said.
The findings are significant because they come from a point in time that’s not well-documented, said Ian Tattersall, a curator in the division of anthropology at the American Museum of Natural History in New York, in an April 6 telephone interview.
That’s the time “just after 2 million years ago when we think that the earliest members of the genus Homo, to which we belong, were evolving,” he said.
Tattersall said he doesn’t think the newly discovered species represents the “actual precursor” to more recent human ancestors. “What these features do is show you can have features of this kind in an archaic kind of hominid that is not a member of the genus Homo,” he said.
Since the first discoveries of the sediba specimens, made in 2008, Berger and his colleagues have found at least two more hominid skeletons at the site, he said yesterday. The bones were discovered along with skeletons of saber-toothed cats, a wild dog, a horse and antelopes among about two dozen species of animals, the scientists reported.
The Cradle of Humankind, located 40 kilometers (25 miles) outside of Johannesburg, is also the place where the more than 2 million-year-old fossil of Australopithecus africanus known as “Mrs. Ples” was found in 1947. Discoveries at the site have yielded insight into human evolution dating back 3.3 million years, according to the Web site of World Heritage, a cultural institution connected to the United Nations.
The latest finding occurred in what was once a deep cave or underground lake, and sediba and animals may have entered in search of water, said Paul Dirks, a structural geologist and professor at James Cook University in Queensland, Australia, and a lead author of one of the papers.
The fossils were probably well-preserved because it’s likely they ended up in a place inaccessible to scavengers, Dirks said.
“Perhaps at the time of their death, the area in which sediba lived experienced a severe drought,” he said. “Animals may have smelled the water, ventured in too deep, fallen down hidden shafts in the pitch dark, or got lost and died.”
Sediba’s overlap of primitive characteristics with more developed features is indicative of the way humans evolved, with a period of possibly 600,000 years in which Australopithecus and Homo co-existed, Tattersall said.
“We’re all brought up to think of our history as a slow, single-minded slog from primitiveness to perfection in some way, and clearly that was not the case,” he said. “We’re one of nature’s many experiments that seems to have succeeded.”
To contact the reporter on this story: Meg Tirrell in New York at email@example.com.